In general, for example, wheel loaders are known as a representative example of wheel type construction machines. In this wheel loader, a front vehicle body is swingably coupled to the front side of a rear vehicle body in a left-right direction, and a working mechanism including an arm and a bucket is mounted to the front vehicle body. On the other hand, an engine, a torque converter, a transmission, a hydraulic pump and the like are mounted on the rear vehicle body, which enables power of the engine to be transmitted to the transmission through the torque converter.
Further, an axle device is provided on each of the front vehicle body and the rear vehicle body to drive/rotate wheels in both left and right sides with connection of the axle devices to an output shaft of the transmission. The axle device is configured of a differential case that is arranged in an intermediate part in the left-right direction and an inside of which is a differential mechanism accommodating room; left and right brake cases that are arranged in both left and right sides of the differential case, the left and right brake cases each being defined by a partition wall to said differential mechanism accommodating room in said differential case, and an internal part of the brake case being formed as a brake mechanism accommodating room; a differential mechanism that is provided in the differential mechanism accommodating room in the differential case and distributes a drive force of the drive source to rotational shafts arranged in the left-right direction; left and right axle shafts that transmit rotations of the left and right rotational shafts of the differential mechanism to the left and right wheels; and left and right brake mechanisms that are provided in the respective brake mechanism accommodating rooms in the left and right brake cases to apply braking to the rotation of the rotational shaft in said differential mechanism.
Here, the brake mechanism is configured of a plurality of rotating discs that are mounted on the rotational shaft and rotate together with the rotational shaft; a plurality of non-rotating discs that are mounted in the brake case in a non-rotating state to face and be across the rotating disc in the left-right direction; and an annular piston that is provided in the brake case to face the non-rotating disc and presses the non-rotating disc on the rotating disc to generate a braking force.
The piston in the brake mechanism is provided with a pin member movable in the left-right direction. On the other hand, the partition wall of the brake case is provided with an annular plate that abuts on the piston member moving together with the piston, a spring member that urges the pin member to a direction opposing the pressing direction of each of the discs by the piston through then annular plate, and a stopper that positions the spring member (for example, refer to Patent Document 1). Thereby, in a case of releasing the pressing force of the piston having pressed each of the discs, it is possible to return back the piston by a prescribed dimension by the urging force of the spring member.